Process of treating sheet metal for drawing and the like



April 1939. H. A. m QQQQQQQ RY 2,153,811

INVENTOR Patented Apr. 1 1, 1939 UNITED "STATES PATE T OFFICE 2.153.011

rnocass or rnnamq snna'r mutton nnawmc arm THE LIKE nan a. Montgomery.Highland rm, M ca. Application Novembe'it 5, use, Serial No. mass:

ing or drawing operations.

Sheet steel, such as ordinarily used for stamping or drawing operations,is frequently not homogeneous throughout and contains portions which areharder than other portions. When submitted to deformingoperations,ridges, high spots 'and low spots are often produced in the article, dueto the softer areas of metal stretching out in'drawing the metal. .Suchirregularities on'the surface of the sheet metal are commonly known asstretcher strains" and are quite apparent. It requires expensivefinishing processes, 15 such as polishing, buillng or the like, toeliminate such defects. 9 that the metal stampings can be used for manypurposes, such as for fenders or q y portions of. an automobile and thelike. In order toeliminate as far as possible such stretcher strainsfrom the sheet metal before it is submitted to the stamping or drawingoperation, it is customary to pass the sheets through a cold rollingmachine known as a roller leveler" or buckler", which conditions themetal so that it may be drawn with greater ease and, when drawn, willhave. fewer surface irregularities. This machine has upper and lowerrows of rolls. The lower row consists of a plurality of spaced rolls instationary bearings, with a common drive. and the upper row consists ofa plurality of adjustable rolls arranged in staggered relation withrespect to the rolls of the lower row. These upper. rolls may beadjustable individually-or in any suitable combinations to give thedesired amount of bending and pressure for the thickness of the metalbeing rolled. The rolls are positioned alternately between the lowerrolls.. In passing the sheet metal through such a machine the metalpasses between the rolls and is caused 40 to take a sinuous path, thusbending each portion of the sheet, both above and below the normal planeof the sheet. If there is any slippage, due

to lubrication, between the, metal and the rolls during the reversebending operation, the surface of the metal is marred. Kerosene or somesimilar light hydrocarbon is ordinarily applied to the sheet that is tobe roller leveled to wash away the dirt and grit and any grease that maybe present on the sheet. Such a light hydrocarbon as I -While such aprocess of treatment of the sheet 55 metal before stamping or drawingaids in the elimination of surface irregularities, it does not entirelyprevent the formation of ridges and high spots. The articles produced bydrawing sheets so treated usually require a further finishing process,such as bufllng, polishing and the like,

[to give the article asmooth surface. Furthermore, in processes now usedthere is considerable drawing, such that the drawn articles producedwill be free from unevenness and surf irregularities and will elongateuniformly and have a smooth finish, so that surface finishing operationsare unnecessary, or greatly lessened.

Another object of the invention is to provide a method of treating thesheet metal prior to drawing, which permits. the metal to be drawn withgreater ease and uniformity, thereby reduc- -ing the amount ofbreakagein the drawing process. 4

a further object of this invention is to provide a composition whichwill not only prevent the formation of surface'irregularitiesin thedraw- 25 ing operation but will act to inhibit corrosion prior to andafter the stamping or drawing operation. a

Other'objects and advantages of this invention will be apparent from thefollowing deso scription of the process.

,According to the present invention it has been found that its sheet ofmetal, such as sheet steel, is treated with a composition comprising asaponiiiable fatty substance containing some'i'ree 35 fatty acid, in asuitable solvent, and the sheet is passed through the rolls of abuckling machine,-

suchcomposition is very effective in preventing stretcher strains and inputting the sheet in condition so that when it is subjected to molecular(a movement during a stamping or drawing operation the finished articlewill have a more continuous smooth surface and require less refinishing.

In the accompanying drawing there is shown 45' diagrammatically abuckling machine consistin of upper rolls I and lower rolls 2 betweenwhich rolls the sheet metal 3 1 .8 9 and by which thesuccessive'portions of the sheet are bent in opposite directions andsqueezed'between the rolls. The treating composition is shown as.applied. to the sheets by spray nozzles 4 and 5. One set of rolls ispreferably vertically adjustable to give the desired amount of bendingand pressure for the thickness of the metal being rolled. In the do IIlnsthemersetofrollsl indicated soadiustablebyscrewsi hichraiselowerbearingblccksmotshown) rollal.

Theliouidtreatingcompositionmaybeasol tion in some hydrocarbon vehicleof a suitable fatty acid. such as oleic, palmitic or arachidic,

or any fatty substance containing some free fatty acid. The vehiclemaybe a mineral oil, such as kerosene, naphtha, or fuel oil, or anyother suitable vehicle that.will not disadvantageously aifect the metaland will spread a film of the fatty acid or fat thereon. It is desirableto have the treating composition contain from about to free fatty acid.

One commercial fatty substance which is readily obtainable and efficientfor use in the treating composition is wool fat, which contains lanolin,degras and recovered grease. Woorfat contains some free fatty acid. Atreating composltion consisting of about 5% to 25% wool fat, andpreferably about dissolved in kerosene or other suitable hydrocarbonvehicle, has been found to be very satisfactory.

The exact action of such composition on the sheet of metal, wherebypassing the sheet through the buckling machine and the stamping ordrawing thereof subsequently is facilitated and a smooth articleproduced, is not known. The fatty acid in the presence of kerosene orsome other suitable solvent apparently finds its way into the pores andinfinitesimal cracks that may be produced in the buckling and squeezingof the metal I as it isbent back and forth in passing through the rolls.

The free fatty acid in the composition decreases the surface tension andincreases the wetting power of the composition, and this may be thereason why the material finds its way into the pores and infinitesimalcracks of the metal as it -is passed through the rolls and squeezedtherebetween.

The metal coming from the buckling machine,

treated with a fatty acid solution as above described, may be drawn moreuniformly and with considerably greater ease, and the drawn article hasa smoother and more polished surface. It has also been found that thedrawing of sheets sotreated produces a smooth condition on the .dies,and that there is considerably less breakage of the sheets in thedrawing operation. The malleability of the metal seems in some measureto be affected.

Another advantage of the present invention is that the sheets of metalmay be run through the buckling machine and stored for a considerableperiod of time before the stamping or drawing operation without rustingor corroding.

The treating composition can be applied to the sheets in any suitableway, such as by immersion of the sheet therein or by spraying itthereon, or applying it to the rolls of the buckling machine.

Furthermore, it will be understood that the present invention is notlimited to the specific details set forth in the foregoing examples,which should be construed as illustrative, and not by way of limitation,and in view of the numerous modifications which may be effected thereinwithout departing from the spirit and scope of this invention, it isdesired that only such limitations be imposed as are indicated in theappended claims. I

What I claim is:

- 1. The process of drawing sheet metal which comprises treating thesheet with a fatty acid in solution, subjecting the sheet to reversebending operations. and drawing the sheet while said treating solutionis disposed on said sheet.

2. The process of drawing sheet metal which comprises preparing themetal by coating surfaces thereof with a light hydrocarbon having about5% to 10% fatty acid in solution, passing the metal while cold betweenrolls which cause reverse bending ofeach portion of the sheet, anddrawing the metal while so coated.

3. The process of drawing sheet metal which co prises treating the metalprior to drawing by app ying a solution of fatty acid to the metal,passing the metal through rolls in such a manner that it is-caused totake a sinuous path, thereby working the solution into the surface ofthe metal, and leaving the solution on the metal for drawing.

4. The process of drawing sheet metal which comprises treating the metalprior to drawing by applying a solution comprising about 5% to of a woolfat in a light hydrocarbon solvent, passing the metal through rolls insuch a manner that it is caused to take a sinuous path, thereby workingthe solution into the "surface of the metal, and leaving the solution onthe metal for drawing;

5. The process of forming drawn articles from sheet metal, whichcomprises passing the sheet metal through rolls which cause it to take asinuous path, while the metal is coated with a solution containing .5%to 10% of free fatty acid in a light mineral oil solvent, and thendrawing the metal while coated with said solution.

6. The process of forming sheet metal articlm by drawing and the like,which comprises preparing the metal by passing the metal while coldbetween rolls which cause reverse bending of each portion of the sheetwhile the metal is coated with a composition comprising a fatty aciddissolved in a light mineral oil, and leaving the coating on the metalfor drawing.

7. The process of forming articles from sheet metal by drawing and thelike which comprises applying a composition comprising a fatty sub-.stance dissolved in a light hydrocarbon vehicle which will spread a filmof the fatty substance onto the surface of the sheet, subjecting thesheet to a reverse bending operation, thereby working the solution wellinto the surface of the sheet, and forming the article while thecomposition has a film of the fatty substance thereon.

8. The process of drawing sheet steel which comprises preparing themetal by applying a light hydrocarbon, containing a small portion of afatty substance in solution, to both sides of the sheet, reverselybending the sheet a plurality of times I and simultaneously rolling thesheet, whereby the physical condition of the sheet is modified toimprove its drawing properties, and drawing the metal with said solutionapplied thereto.

9. In the process of drawing sheet metal to produce an article having arelatively smooth polished surface, the steps of coating the sheet witha solution of a fatty acid in a light hydrocarbon solvent, successivelybending the metal in one direction and then in the other direction aplurality of times while simultaneously squeezing the metal, andallowing the coating to stay on the metal until drawn.

10. The process of producing drawn sheet metal articles having a smoothfinish free from irregularities and defects, which comprises applying atreating solution of a fatty substance dissolved in a light hydrocarbonto the-surface of the sheet, thoroughly working the solution into thesheet surface by reverse bending thereof, and drawing the sheet to formthe drawn article, while said treating solution is applied thereto.

1. The process of producing drawn lsheet metal articles having a smoothfinish free from irregularities and defects, which comprises applying atreating solution of about 5 to 25% of a fatty substance dissolved in alight hydrocarbon to the surface of the sheet, thoroughly working thesolution into the sheet surface by reverse bending thereof, and drawingthe sheet without removing the treating solution.

HARLEY A. MONTGOMERY.

